The present invention relates to a device for preparing beverages of the type having a closed compartment, an open compartment, an ascension pipe connecting the compartments and a filtering device between the ascension pipe and the open compartment. Further, the invention relates to a method for preparing beverages using the above mentioned device, where liquid is brought to the desired infusion temperature in the closed compartment and is forced by the steam pressure through the ascension pipe and the filtering device to the open compartment containing the aromatic carriers, after which the steam from the remainder of the liquid in the closed compartment condenses in the liquid in the open compartment thereby heating the mixture of liquid and the aromatic carriers to the desired infusion temperature for some time, after which the closed compartment is allowed to cool thereby decreasing the pressure in the closed compartment so as to bring back the beverage by suction of the beverage through the filter and the ascension pipe to the closed compartment leaving the residuals of the aromatic carriers in the open compartment.
Such device and method is known from e.g. DK 90776 and 98310 and was developed for about forty years ago. Common to those prior devices is, that for heating the contents of the device an external heating source is needed. Such heating source can be achieved using a spirit lamp or a hotplate, but for some applications such external heating sources might be, inappropriate. The use of open fire might increase the. risk for fire and other external heating sources with their up-turned hot surfaces might also increase the risk for burning the operating persons or simply melting plastics items unintendedly left on such hot surfaces. Further, the infusion time is either fixed being decided by the distance between the lower orifice of the ascending pipe and the bottom of the closed compartment or left to the user to estimate.
It is commonly known to use liquid heating vessels energized by electricity, and such liquid heating vessel is disclosed in EP 0841030 A1. The novel aspect there is, that a heating element is fixed with a sealing flange to the underside of a metal plate which closes the bottom of the vessel. Such heating vessels are because of the sealing means inappropriate for preparing beverages as disclosed in the ingress of the specification, and the inventor has consequently as a goal to solve the disadvantages of the state of the art, thereby minimizing the risks of the prior art.
To this end the inventor has suggested a device as mentioned in the ingress of the specification, where the bottom of the closed compartment is comprising at least two levels, one level of diminished elevation in a relatively small area around the lower orifice of the ascension pipe, the level of which is at least below the other elevated level of a relatively large area, said large area being equipped with electrical heating means controlled by switching means and at least one temperature sensitive means for controlling the switching means, said large area of the bottom being surrounded by a rim for holding a residual of liquid.
With the device according to the invention the inventor has eliminated the above mentioned risks of fire and burning and further, some more advantages like the possibility to control the infusion time have been achieved in the multilevel bottom and the electrical operation of the device.
From EP-O 292649 A1 it is known to have the bottom of the closed compartment split in two sections, an upper and a lower section, where each section has a heating element. This device is aimed at making tea by varying the distance above the lower bottom of the ascension pipe""s orifice in order to adjust the infusion time for the tea during which the water at the lower level evaporates. This prior art, however, is not suited for making e.g. coffee and it is costly to produce, as it contains a relatively large number of parts, particularly the moveable ascension pipe. Further, the ascension pipe must be of a type which is sealingly moveable in order to control the flow of the water/tea. Also, the lower level is equipped with a heating element which means that only boiling water will ascend through the ascension pipe. Thereby the temperature of the water in the upper/open compartment will inevitably never approximate the boiling temperature of the water and the infusion will not meet the goal of performing the infusion at the optimum temperature of the aromatic carriers.
In an embodiment of the invention it is suggested that the heating means comprise at least two different heating means, for differentiated heating supply to the closed compartment. If, further, a temperature sensitive means is functionally connected to a switching means for each heating means, it is possible within narrow limits to keep the beverage at a preferred temperature for drinking, as such temperature control is more adequately achieved by electrical operation than by e.g. a spirit lamp or a hotplate. It should here be understood, that the switching means are mechanically operated, but the switching means can as well be electronically operated. To this end, it is most appropriate having the electronically switching means controlled by at least one micro processor, which is not shown in detail in the drawings.
In another embodiment of the invention it is suggested that the device for preparing beverages comprise means for varying the infusion time, where the variation of the infusion time is controlled electronically by the micro processor through delayed switching on of at least one of the heating means during the cooling-off of the closed compartment.
In still another embodiment a variation of the infusion time is achieved by varying the effective height of the rim, so as to vary the contents of the residual liquid to be evaporated. To this end it is suggested, that a cylindrical lining on the inside of the rim is pivotally and sealingly secured to the rim being of varying height along the circumference, said lining itself being of varying height. Of course, the rim could as well be a lining in a pivotable regulation cylinder, but it seem to be most practical to use the pivotable lining.
The invention further relates a method for preparing beverages using the device according to the invention, the method being of the type as mentioned in the ingress of the specification, where the inventor suggests the following steps:
i. using the heating means of the relatively large area for:
a. heating the liquid in the closed compartment, thereby increasing the pressure in said closed compartment and forcing the liquid to the open compartment and leaving a residual of liquid behind the rim surrounding the relatively large area equipped with the heating means,
b. evaporating the residual of liquid behind said rim, thereby maintaining the pressure in the closed compartment by exhausting the steam through the ascension pipe to the open compartment, where the steam condenses in the mixture of liquid and aromatic carriers, heating the mixture to a desired infusion temperature, which is maintained until the evaporation is finished, the duration of which is decided by the volume of the residual of liquid, or the effective height of the rim enclosing the volume of liquid,
c. heating the relatively large area of the closed compartment, thereby increasing the temperature until the temperature sensitive means react and switch the circuit supplying the heating means, and
ii. by switching off the circuit supplying the heating means of the relatively large area leaving the closed compartment,
a. to cool, decreasing the pressure in the closed compartment to a vacuum or depression;
b. to use the vacuum to perform a suction of the beverage from the open compartment through the filter and the ascension pipe into the closed compartment, and
c. to leave the carriers of the aroma in the open compartment;
iii. switching the heating means to a power state being sufficient to keep the beverage at the desired temperature.
By initiating the final switching iii at a delayed time, the returning of the beverage can be advanced so as to shorten the infusion time. This aspect might serve to allow the user to choose a different taste of the beverage.